Quick-couplers are frequently used with construction machines such as hydraulic excavators or articulated grippers such as wood handling machines or demolition units or similar material transfer machinery for coupling different tools such as rakers, clamshell grapples or demolition shears to an excavator arm or similar tool guides such as articulated arm booms in order to be able to use different tools without long changeover times. Such quick-couplers can in particular have two mutually spaced apart locking axles as locking elements at a coupling part, whereas the other coupling part, in particular the coupling part at the excavator arm side can have a preferably hook-shaped coupling mount for hooking at a first one of the two locking axles and a locking mount for locking at the second locking axle. After hooking the first locking axle in the coupling mount, the two coupling parts can be pivoted with respect to one another, wherein the locking axle seated in the coupling mount forms the pivot axle so that the second locking axle moves or is pivoted into the locking mount where the named second locking axle can then be locked by a locking element such as an extendable wedge so that it is simultaneously also no longer possible to move the first locking axle out of the coupling mount. The named locking axles at the one coupling part can in this respect be formed by locking pins which can extend at the corresponding coupling part, in particular in parallel with one another, with optionally instead of such pins also other structural parts of the coupling part such as projecting noses, axle pivots, engagement stubs in the form of projections or recesses, for example in the form of pockets, being able to serve as the locking part, however, and being shape-matched to the coupling mount or to the locking mount of the other coupling part.
It has already been proposed for the prevention of the first locking axle from being released from the coupling mount again on the named pivot process after the hooking of the named first locking axle into the coupling mount to associate a securing element, for example in the form of a spring-loaded snap-in wedge, to the coupling mount, with the snap-in wedge capturing the locking axle on the hooking of the locking axle into the coupling mount and securing it in the coupling mount. On the moving of the locking axle into the coupling mount, the securing snap lock is pressed back until the completely hooked-in position is reached so that the securing snap lock can snap back again and can block the exit path from the coupling mount. To be able also to move the first locking axle or to unhook it from the coupling mount on the removal of a tool after the unlocking of the locking mount, this securing element has to be released again or has to be moved into its releasing position again. This can take place with pressure medium actuation, for example by a simply acting pressure medium cylinder which can move the securing element back into the releasing position against its spring pre-loading into the locking or blocking position. A climbing down of the machine operator or a manual actuation can hereby be avoided.
To make the actual locking mechanism, which transmits force in operation and by which the second locking element, for example in the form of a locking axle, is fixed or locked in the locking mount, independent of the actuation of the securing element associated with the coupling mount, the enabling or release of the named securing element at the coupling mount is effected by a separate pressure medium circuit which can be controlled independently of or is configured separately from the pressure medium circuit for actuating the locking mechanism. This decoupling is carried out to prevent problems at the securing element from being able to spread to the actual locking mechanism and from being able to effect an unwanted release of the coupling locking in operation. Such problems could, for example, be pressure losses at sealing elements, for example, which are provided in pressure circuit sections leading to the securing element of the coupling mount. The document EP 1852555 A2, for example, shows such a quick-coupler having mutually decoupled, separate pressure circuits for the actuation of the locking mechanism and for the unlocking of the securing element at the coupling mount.
Since in practice in the past quick-couplers of the named type, which were sold in large volumes and which are still in use today, were/are not provided with such an additional securing element at the coupling mount, it would be desirable not only to provide such an additional securing means at the coupling mount with new devices, i.e. new quick-couplers, but also to be able to retrofit them to old quick-couplers. The solution shown in the named document EP 1852555 A2 is admittedly generally also suitable for retrofitting already existing quick-couplers, but it requires three hydraulic connections due to the separate pressure circuit for actuating the securing element of the coupling mount, namely two connections for actuating the actual locking mechanism and a further pressure connection for unlocking the securing element of the coupling mount. In many cases, however, only two hydraulic connections are present at existing devices so that the retrofitting with such an additional security at the coupling mount is often not possible.